Thiazolidinedione compounds

ABSTRACT

The compounds are 5-(4-substituted benzyl)thiazolidine-2,4-diones, enantiomers, diastereoisomers and pharmaceutically tolerable salts thereof, useful for treating conditions of insulin-resistance and/or non insulin-dependent diabetes. A compound disclosed is: .(R,S)-5-{4-[2-benzofuran-2-yl)carbonylamino)ethyl]benzyl}thiazolidine-2,4-dione.

This application is a continuation-in-part of the application Ser. No. 08/133,898 filed Oct. 12, 1993, now abandoned.

The present invention relates to new thiazolidinedione compounds, a process for their preparation and pharmaceutical compositions containing them.

It relates more especially to:

thiazolidinedione compounds of formula I: ##STR1## wherein: Ar represents:

a) a polymethylene ring containing from 5 to 7 carbon atoms which is optionally substituted by one or more alkyl radicals having from 1 to 5 carbon atoms,

b) a mono-, bi- or tri-cyclic hydrocarbon radical such as, for example, a phenyl, naphthyl, fluorenyl, dibenzocycloheptenyl or biphenylyl radical, each of which is optionally mono- or poly-substituted by a halogen atom, such as, for example, a fluorine, chlorine or bromine atom, a trifluoromethyl radical, a straight-chain or branched alkyl, alkoxy or alkylthio radical each having from 1 to 5 carbon atoms, an acyloxy radical, a hydroxy radical or a radical of the formula ##STR2## in each of which R₁ and R₂, which are the same or different, each represents a hydrogen atom, or a straight-chain or branched alkyl radical having from 1 to 5 carbon atoms, or R₁ and R₂, together with the nitrogen atom to which they are bonded, represent a heterocycle having from 4 to 7 ring members optionally including (in addition to the nitrogen atom) an oxygen or sulphur atom, or

c) a mono-, bi- or tri-cyclic heterocyclic radical containing 1 or 2 hereto atoms selected from nitrogen, oxygen and sulphur atoms, such as, for example, a furyl, thienyl, pyrrolinyl, pyridyl, pyrazinyl, oxazolyl, thiazolyl, indolyl, imidazolyl, chromanyl or xanthenyl radical, each of which is optionally substituted by an oxo radical and/or by one or more halogen atoms or alkyl radicals (having from 1 to 5 carbon atoms) or phenyl radicals, each phenyl radical itself optionally being substituted by one or more halogen atoms or trifluoromethyl radicals or alkyl or alkoxy radicals each having from 1 to 5 carbon atoms;

A represents: a single bond, a hydrocarbon chain having 2 or 3 carbon atoms and including a double bond, or a chain of the formula --(CH₂)_(m) --, ##STR3## --O--(CH₂)_(m) -- or --S--(CH₂)_(m) -- wherein: m is an integer from 1 to 3 and R' and R", which are the same or different, each represents a hydrogen atom or a straight-chain or branched alkyl radical having from 1 to 5 carbon atoms;

X represents an oxygen atom, --CONR-- or --SO₂ NR-- wherein R represents a hydrogen atom or a straight-chain or branched alkyl radical having from 1 to 5 carbon atoms and optionally including a double bond,

or, when A represents a single bond and Ar represents a phenyl radical, R may also represent a carbonyl radical bonded to Ar by its free bond such that Ar--A--X together form a phthalimido radical;

B represents a saturated hydrocarbon chain having from 1 to 6 carbon atoms which is optionally branched and/or substituted by a hydroxy radical or an oxo radical;

and also the enantiomers and, when B is branched, the corresponding diastereoisomers.

The prior art is illustrated especially by the patent applications EP 008203, WO 8607056, EP 207581, WO 8504171 and WO 9207850 which relate to thiazolidine-2,4-dione compounds which can be used as antidiabetic agents.

Apart from the fact that the compounds of the present invention are new, they differ from the previously known thiazolidine-2,4-dione compounds in the intensity of their pharmacological properties.

Insulin resistance and the lack of secretion of insulin are responsible for the glucose intolerance observed in patients having non-insulin-dependent diabetes.

The therapeutic agents currently available essentially allow correction of the lack of insulin secretion without necessarily improving the sensitivity to insulin of peripheral tissues (muscles, adipose tissue).

Thiazolidine-2,4-dione compounds are capable of causing a reduction in glycaemia and of improving glucose tolerance in non-insulin-dependent diabetic models without causing an increase in the secretion of insulin.

The compounds of the present invention have the advantage of being especially powerful (more especially compared with ciglitazone, a reference compound belonging to the same chemical class) whilst at the same time not exhibiting harmful haematological effects, as will be demonstrated by the pharmacological study described hereinafter.

The compounds of the present invention may thus be used in the treatment of conditions of insulin resistance and/or of non-insulin-dependent diabetic conditions, making it possible to obtain a better control of glycaemia but with a reduced level of circulating insulin. The prevention of that relative hyperinsulinaemia, associated with a reduction in circulating triglycerides resulting from the action of those compounds, may assist in reducing the risks of macroangiopathy.

The same compounds may furthermore be used in the treatment of hypertension in older patients exhibiting insulin resistance which may or may not be associated with other metabolic anomalies.

The present invention relates also to pharmaceutical compositions comprising as active ingredient a compound of formula I or a physiologically tolerable salt thereof, mixed with or in association with one or more appropriate pharmaceutical excipients.

The pharmaceutical compositions so obtained are generally in dosage form containing from 100 to 200 mg of active ingredient. They may, for example, be in the form of tablets, dragees, gelatin capsules, suppositories or injection or drinkable solutions, and may be administered by the oral, rectal or parenteral route.

The dosage may vary, especially in accordance with the age and weight of the patient, the administration route, the nature of the disorder, and associated treatments, and ranges from 100 to 200 mg of active ingredient from 2 to 3 times per day.

The present invention relates also to a process for the preparation of compounds of formula I characterised in that:

either,

A) a compound of formula II: ##STR4## wherein: Ar, A, X and B are as defined hereinbefore and

Hal represents a chlorine or bromine atom, is reacted with thourea ##STR5## and the imine so obtained of formula III: ##STR6## wherein Ar, A, X and B are as defined hereinbefore, is hydrolysed; or, B) a compound of formula IV:

    Ar--A--X'                                                  (IV)

wherein:

Ar and A are as defined hereinbefore and

X' represents COCl, SO₂ Cl, an activated ester or --(CO)₂ O,

is reacted with a compound of formula V: ##STR7## wherein: B is as defined hereinbefore and

R' represents a hydrogen atom or a straight-chain or branched alkyl radical having from 1 to 5 carbon atoms.

Method A, described by T. Sohda et al, Chem. Pharm. Bull., 30 (10) 3580-3600 (1982), is especially suitable for the preparation of compounds I if carried out in an appropriate solvent such as, for example, methanol, ethanol, sulfolane® or dimethylformamide, heating the mixture of compound II and thiourea at 100°-120° C. for from 6 to 10 hours and then hydrolysing compound III by means of a strong acid, such as HCl or H₂ SO₄.

The starting materials of formula II were prepared from amines of formula: ##STR8## which were themselves obtained by hydrogenating corresponding nitrated compounds under a pressure of 3×10⁵ Pa in the presence of Raney nickel.

Method B is advantageously carried out by reacting the compounds IV and V at a temperature of 20°-25° C. for from 8 to 15 hours in a suitable solvent, such as, for example, tetrahydrofuran, dimethylformamide or acetonitrile, alone or in the form of a mixture, in the presence of an acceptor for the acid formed during the course of the reaction.

That acceptor may be, for example, triethylamine or an excess of the compound V used for the synthesis. Furthermore, compounds of formula I wherein the group Ar is substituted, inter alia, by a hydroxy radical, may also be prepared by hydrolysing corresponding acyloxy compounds in the presence of sodium hydroxide solution.

Compounds I prepared in accordance with method A or B may be purified by crystallisation from appropriate customary organic solvents or by flash chromatography on an Amicon silica support (35-70μ) using as eluant appropriate solvents such as: CH₂ Cl₂, CH₂ Cl₂ /acetone (95:5), toluene/ethanol (95:5), under a pressure of 0.5 to 1 atmosphere of nitrogen.

The compounds of formula I may be converted into addition salts with acids, which salts, as such, form part of the invention. There may be mentioned as acids that can be used for the formation of those salts, for example, in the mineral series, hydrochloric, hydrobromic, nitric, sulphuric and phosphoric acid and, in the organic series, acetic, propionic, maleic, fumaric, tartaric, oxalic, benzoic, methanesulphonic and isethionic acid.

The following Examples illustrate the present invention. Unless specified otherwise, the melting points are determined using a Kofler hot plate.

EXAMPLE 1 5-{4-[2-(2-methoxy-5-chlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione ##STR9##

A mixture of 4.1 g of methyl 3-{4-[2-(2-methoxy-5-chlorobenzamido)ethyl]phenyl}-2-chloropropionate (oil) and 1.52 g of thiourea are heated for 10 hours at 120@C in 40 ml of sulfolane®. The imine formed is hydrolysed by adding 14 ml of 2N HCl to the mixture and heating the whole at 100° C. for 8 hours. When the reaction is complete, the whole is diluted with 600 ml of water and the aqueous portion is decanted off. The gummy product is extracted with CH₂ Cl₂ and the organic solution is washed with water. After evaporation of the solvent, the residue is purified on 90 g of silica by flash chromatography using a mixture of CH₂ Cl₂ and methanol (95:5) as eluant. The evaporated eluates yield 2.6 g of the desired compound in crystallised form, m.p.: 182° C.

EXAMPLE 2 (R,S)-5-{4-[2-(4-hydroxy-3,5-di-tert-butylbenzamido)ethyl]benzyl}thiazolidine-2,4-dione ##STR10##

1.9 g of 1,1-carbonyldiimidazole is added to a solution of 3 g of 4-hydroxy-3,5-di-tert-butylbenzoic acid in 150 ml of anhydrous tetrahydrofuran and the solution is stirred at room temperature for 8 hours. 3 g of 5-[4-(2-aminoethyl)benzyl]thiazolidine-2,4-dione (melting at 200° C.) are then added and the mixture is stirred at room temperature for 15 hours. The solvent is then evaporated off and the residue is taken up in a mixture of 10% Na₂ CO₃ in CH₂ Cl₂. The precipitate is filtered and then purified by flash chromatography on 180 g of silica using a mixture of CH₂ Cl₂ and methanol (97:3) as eluant.

After evaporation of the eluates, 3 g of the desired compound in amorphous form are collected. The 5-[4-(2-aminoethyl)benzyl]thiazolidine-2,4-dione starting material was prepared by the method according to SOHDA et al from methyl 3-[4-(2-acetamidoethyl)phenyl]-2-chloropropionate (oil).

EXAMPLE 3 (R,S)-5-{4-[2-(salicyloylamino)ethyl]benzyl}thiazolidine-2,4-dione ##STR11##

2.3 g of acetylsalicyloyl chloride are added to a solution of 3 g of 5-[4-(2-aminoethyl)benzyl]thiazolidine-2,4-dione and 1.16 g of triethylamine in 50 ml of anhydrous dimethylformamide and the mixture is stirred at room temperature for 15 hours.

The dimethylformamide is then evaporated off and the residue is taken up in CH₂ Cl₂ and water.

The organic phase is separated off and then evaporated under reduced pressure. 5.3 g of an oily residue are obtained which are chromatographed on 170 g of silica using a mixture of CH₂ Cl₂ and acetone (90:10) as eluant. Evaporation of the eluates leaves 3 g of amorphous product which is dissolved in 50 ml of ethanol and then hydrolysed in the presence of 8.5 ml of N NaOH at room temperature for 5 hours. The solvent is then evaporated off, the product is taken up in N HCl and the resulting white crystals are suction-filtered.

1.9 g of the desired compound are obtained. M.p.: 184° C.

EXAMPLES 4 TO 51

The following compounds were prepared by operating analogously to the methods described above:

4)5-{4-[2-(phthalimido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 180° C.

5) 5-{4-[2-(diphenylacetylamino)ethyl]benzyl}thiazolidine-2,4-dione, amorphous product.

6) (R,S)-5-{4-[2-(3,3-diphenylpropionamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. 148° C.

7) (R,S)-5-{4-[2-(2,5-dimethoxybenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 182° C.

8) (R,S)-5-{4-[2-(4-methoxyphenylsulphamoyl)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 143° C.

9) (R,S)-5-{4-[2-(3-trifluoromethylbenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 130° C.

10) (R,S)-5-{4-[2-(3,4-dichlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 170° C.

11) (R,S)-5-{4-[2-(phenylacetylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 128° C.

12) (R,S)-5-{4-[2-(phenoxyacetylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 138° C.

13) (R,S)-5-{4-[2-(cyclopentylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 154° C.

14) (R,S)-5-{4-[2-(fur-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 150° C.

15)(R,S)-5-{4-[2-(5-methyl-1,2-oxazol-3-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 148° C.

16) (R,S)-5-{4-[2-(2-hydroxy-5-chlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 242°-244° C.

17) (R,S)-5-{4-[2-(2-amino-5-chlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 196°-200° C.

18) (R,S)-5-{4-[2-(2-dimethylamino-5-chlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 162°-164° C.

19) (R,S)-5-{4-[2-(5-methoxyindol-2-ylcarbonylamino)-ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 232°-236° C.

20) (R,S)-5-{4-[2-(pyrid-3-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 238°-240° C.

21)(R,S)-5-{4-[2-(pyrid-4-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 278°-280° C.

22) (R,S)-5-{4-[2-(cinnamylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 76°-78° C.

23) (R,S)-5-{4-[2-(3-phenylthiopropionamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 76°-78° C.

24) (R,S)-5-{4-[(R,S)-2-(2,5,7,8-tetramethyl-6-hydroxychroman-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, amorphous product.

25) (R,S)-5-{4-[2-(pyrazin-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 198°-200° C.

26) (R,S)-5-{4-[2-(pyrid-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 160° C.

27) (R,S)-5-{4-[2-(indol-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 256° C.

28) (R,S)-5-{4-[2-(2-dimethylaminobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 180° C.

29) (R,S)-5-{4-[2-(2-piperidino-5-chlorobenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 164°-166° C.

30) (R,S)-5-{4-[2-(fur-3-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 176°-178° C.

31) (R,S)-5-{4-[2-(5-methyl-2-phenyloxazol-4-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 178°-180° C.

32) (R,S)-5-{4-[2-(5-methyl-2-phenyloxazol-4-ylacetylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 146°-150° C.

33) (R,S)-5-{4-[3-(2-methoxy-5-chlorobenzamido)propyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 142° C.

34) (R,S)-5-{4-[2-(2-methoxy-5-trifluoromethylbenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap) with decomposition >160° C.

35) (R,S)-5-{4-[2-(thien-2-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 150°-152° C.

36) (R,S)-5-{4-[(5-chloro-2-methoxybenzamido)methyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 150°-152° C.

37) (R,S)-5-{4-[2-(5-chloro-2-methoxyphenylacetamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 116°-118° C.

38) (R,S)-5-{4-[2-(4-amino-5-chloro-2-methoxybenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap) of the corresponding hydrochloride: 125°-130° C.

39) (R,S)-5-{4-[1-oxo-2-(5-chloro-2-methoxybenzamido)-ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 190°-192° C.

40) (R,S)-5-{4-[1-hydroxy-2-(5-chloro-2-methoxybenzamido)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 175°-178° C.

41) (R,S)-5-{4-[2-(3,5-di-tert-butyl-4-hydroxyphenoxy)-ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 118°-120° C.

42) (R,S)-5-{4-[2-(3-ethyl-4-methyl-2-oxo-3-pyrrolin-1-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 178°-180° C.

43) (R,S)-5-{4-[2-(3-(3,4-dimethoxyphenyl)prop-2-enoylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 178°-180° C.

44) (R,S)-5-{4-[2-(3-(3,4-methylenedioxyphenyl)prop-2-enoylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 155°-157° C.

45) (R,S)-5-{4-[2-(xanthen-9-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 138°-140° C.

46) (R,S)-5-{4-[2-(2,2-(2,6-dimethylphenyl)acetylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p.: 182° C.

47) (R,S)-5-{4-[2-(10,11-dihydro-5H-dibenzo[a,d]cyclohepten-5-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 180°-182° C.

48) (R,S)-5-{4-[2-(3-(4-hydroxy-3-methoxyphenyl)prop-2-enoylamino)ethyl](benzyl}thiazolidine-2,4-dione, m.p. (cap): 172°-176° C.

49) (R,S)-5-{4-[2-(fluoren-9-ylcarbonylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 180°-184° C.

50) (R,S)-5-{4-[2-(3-(4-acetoxy-3-methoxyphenyl)prop-2-enoylamino)ethyl]benzyl}thiazolidine-2,4-dione, m.p. (cap): 135°-140° C.

EXAMPLE 51 (R,S)-5-{4-[2-benzofuran-2-yl carbonylamino)ethyl]benzyl}thiazolidine-2,4-dione ##STR12##

3.25 g (0.02 mole) of 2-benzofuryl carboxylic acid, 5 g of (R,S)-5-[4-(2-amino ethyl)benzyl]thiazolidine-2,4-dione, 100 ml of dimethylformamide and 11.5 g of N-ethylmorpholine are mixed in a three necked flask. Then, the mixture is cooled to 5° C. and a solution at 50% of 17.8 g of 1-propane phosphonic acid anhydride in CH₂ Cl₂ is added in 30 minutes. The reaction mixture is stirred at 5° C. for 2 hours then at room temperature for 20 hours, then concentrated to dryness. The residue is taken off in CH₂ Cl₂. The solution is washed with a N-solution of HCl then with water and with a saturated solution of Na₂ CO₃ ; then dried over sodium sulfate and concentrated to dryness. The residue is triturated in a mixture of isopropylic ether and ethanol (about 90/10). A crystallisation is observed. The crystals are suction-filtered, washed with isopropylic ether and dried at 60° C. under a pressure of about 67 Pa.

3.9 g of the desired compound are obtained. m.p. (cap): 162°-164° C., Yield: 49%.

EXAMPLE 52 PHARMACOLOGICAL STUDY

A/ Study of the activity of the compounds of the invention on a non insulin-dependent diabetic model (NIDDM)

The animals (ob/ob mice) are treated each day, for 4 days, by the oral administration of the compounds of the invention suspended in a 20% Senegal gum solution.

Before and after treatment, that is to say on d0 and on d5, blood is taken by piercing the orbital sinus and the glycaemia is determined.

Table 1 shows the doses of the different compounds that need to be administered to obtain the same hypoglycaemic effect (base 100).

                  TABLE 1                                                          ______________________________________                                         Doses causing the same hypoglycaemic effect                                    in ob/ob mice                                                                              Dose mg/kg/day                                                                              Hypoglycaemic                                         Compounds   for 4 days   activity                                              ______________________________________                                         Ciglitazone 50-100       100                                                   Example 1   ≦10   100                                                   Example 3   25           100                                                   Example 4   10           100                                                   Example 6   10           100                                                   Example 7   25           100                                                   Example 14  10           100                                                   Example 15  25           100                                                   Example 25  10           100                                                   Example 28  10           100                                                   Example 33  25           100                                                   Example 35  20           100                                                   Example 36  20           100                                                   Example 40  50           100                                                   Example 41  50           100                                                   Example 43  25           100                                                   Example 44  10           100                                                   Example 45  15           100                                                   Example 46  40           100                                                   Example 51    1.1        100                                                   ______________________________________                                    

B/ Study of the activity of the compounds of the invention on a model having reduced glucose tolerance associated with hyperinsulinaemia and hyperlipaemia. The animals (Zucker Fa/Fa male rats) are treated each day, for 10 days, by the oral administration of the compounds of the invention at a dose of 5 mg/kg/day suspended in a 20% Senegal gum solution. On the 11th day the animals are sacrificed and blood is collected in order to determine glycaemia, plasma triglycerides and immuno-reactive insulin. The animals are also weighed before and after treatment.

Under those conditions the compounds of the invention do not have any influence on the level of circulating glucose but decrease the level of triglycerides (TG) and free fatty acids (FFA) in the plasma and also the level of immuno-reactive insulin. The activity is the same as, or superior to, that of other reference thiazolidinedione compounds.

                  TABLE 2                                                          ______________________________________                                         Pharmacological study of Zucker Fa/Fa male rats                                       Dose                                                                           (mg/                                                                           kg/day                                                                               Weight  Glycaemi Plasma                                                  for   ΔP %                                                                             a        insulin                                                                              TG   AGL                                          10 days                                                                              d.sub.11 -d.sub.1                                                                      (%)      (%)   (%)  (%)                                   ______________________________________                                         Control  0       +100    100    100   100  100                                 Pioglitazone                                                                            5       +320    115    49    35   57                                  Example 1                                                                               5       +112    113    71    94   83                                  Example 4                                                                               5       +132    108    72    78   108                                 Example 28                                                                              5       +103    99     75    89   110                                 ______________________________________                                    

Administered per os to male SDCD rats weighing 175 g, contrary to pioglitazone the compounds are without effect on the specified elements of the blood and the plasma volume:

                  TABLE 3                                                          ______________________________________                                         (control values = 100)                                                         Duration of                                                                    treatment:                                                                              White     Red       Haemato- Haemo-                                   8 days   corpuscles                                                                               corpuscules                                                                              crit     globin                                   ______________________________________                                         Pioglitazone:                                                                           -46%      -37%      -26%     -29%                                     100 mg/kg/d                                                                    Example 1:                                                                     100 mg/kg/d                                                                             -6%       -2%       +11%     +11%                                     250 mg/kg/d                                                                             -4%       -11%      +4%      +4%                                      Example 51                                                                              0         0         +2%      +2%                                      100 mg/kg/d                                                                    ______________________________________                                     

We claim:
 1. A thiazolidinedione compound selected from those of formula I: ##STR13## wherein: Ar represents:a mono-, bi- or tri-cyclic heterocyclic ring containing besides carbon atoms only 1 or 2 heteroatoms selected from nitrogen, oxygen and sulphur, which is optionally substituted by one oxo and/or by one or more halogen or alkyl (having from 1 to 5 carbon atoms inclusive) or phenyl, itself optionally being substituted by one or more halogen, trifluoromethyl or alkyl or alkoxy each having 1 to 5 carbon atoms inclusive; A represents: a single bond, or a chain of the formula --(CH₂)_(m) -- wherein:m is an integer from 1 to 3 inclusive; X represents --CONR-- or wherein R represents hydrogen or straight-chain or branched (C₁ -C₅) alkyl optionally including a double bond, B represents a saturated (C₂ -C₆) hydrocarbon chain;or its enantiomers or diastereoisomers, as well as its addition salts with a pharmaceutically acceptable acid.
 2. A compound of claim 1 which is: (R,S)-5-{4-[2-benzofuran-2-yl)carbonylamino)ethyl]benzyl}thiazolidine-2,4-dione.
 3. A pharmaceutical composition, useful for treating conditions of insulin resistance and/or non insulin-dependent diabetes which may or may not be associated with hypertention, comprising as active ingredient an effective amount of at least one compound as claimed in claim 1 together with one or more pharmaceutically-acceptable excipients.
 4. A method for treating a mammal afflicted with conditions of insulin resistance and/or non insulin-dependent diabetes which may or may not be associated with hypertension, comprising the step of administering to the said mammal an amount of a compound of claim 1 which is effective for the alleviation of the said condition. 